We’ve been using primarily Flash 7 and then 9 for delivery of video over the past few years. Flash was simply the simplest way to deliver content to the largest audience. One main factor, was the processor speed of the computer that was playing the content back. if older, slower cpus were the primary audience you wanted to use the older compression format, named Spark, in order to guarantee good quality playback.
Over the past 15 months we’ve transition to HTML5 based delivery with a flash fall back because of the mix learning audience we have now with various clients we use this to deliver to the entire mobile (smartphones) spectrum including iOS, Android and other flavors of OS. We have 2 magic ingredients:
1. The H264 Codec which is part of the mpeg4 codecs. We started using this in the past couple of years for quick compression and delivery to clients that needed to review content, primarily via QuickTime platform. When Flash 9 was introduced, it adopted the H264 codec and allowed us than to transition to delivery of content within Flash 9 or higher players and deliver amazing quality, at smaller sizes.
2. HTML5 there are several codecs (compression/decompression algorithms) that HTML5 supports based on the browser and OS. Apple uses H264 along with Microsoft and with the combination of Flash 9 we can now deliver content to all platforms without having to worry about compressing to multiple formats/platforms etc.
This has been great and has simplified our workflow from delivery of reviews to final content that is viewed by our client’s audiences. We’ve utilized
JWPlayer from
http://www.longtailvideo.com which offers the ability to first deliver via Flash and if not available it will automatically switch to HTML5. This has been the perfect system for us to integrate into our developments and offer hundreds of hours of content to thousands of users we support in various learning solutions.
Understanding the Video/Audio Compression Process – Tips
Within our workflow we divide video and audio into 4 main steps.
1. Video / Audio Assets
It all starts with capturing the content. Whether you are working with a internal group, your own team or a 3rd party it is always important to get the final assets on a hard drive at the highest quality possible. This will allow you to full control over compression and add the bonus of allowing you to recompress in the future when new technologies or codecs are introduced or optimized. Hard drives continue to drop in price, you can now get 3 terabytes for less than $150. Based on the quality size and compression you are using you can store 2-10 hours of content on the drive.
2. Compression
Here’s where the fun starts, it’s gotten easier and easier to compress content with the latest tools whether free or full-featured tools allow you to easily drag and drop a setting, click compress and squeeze your content to the optimal size.
First, when you are shooting your video, there are several formats and sizes that you can shoot at today. Most video cameras are shooting at HD which offers a 1920 x 1080 pixel size. This is a high-res format and you can notice every little detail of your content. Typically we shoot and capture at this quality and then size down the assets to make it easier to work with in editing.
What’s nice is that you can HD or SD quality from most digital cameras as well as smartphones today, so the content you are capturing looks amazing.
Next step is to select a size for compression. The following graphic shows some typical guidelines and sizes that we start with. Today, whether you use Flash, HTML5 or other format you can basically deliver in any size and format. So your video can be delivered 16×9, 4×3 or any other aspect ratio you can think of which gives you a lot of creative license.
Here’s one of my favorite deliverables, where you deliver video as a additional learning object to enhance the main content which in this sample is text based.
When capturing your video, it is typically shot at 29.97 frames per second (FPS). When you go to compression, we typically compress the frame rate to 10-15 fps. This allows for a much smaller file size and easier to deliver to your audience.
You also want to determine your key frames. Key frames are used when scrubbing your video forward or back ward using the shuttle play bar. If you don’t have enough, you’ll notice inconsistent behavior and skipping while you move the shuttle bar. We use 4 times the frame rate to define the number of key frames. So if our frame rate is 15, our key frames would be 90 (4 x 15).
The other variable we want to focus on is the data rate of your video. We typically target 800 – 1200 kilobits per second. If you have good quality video this will give you great compression without noticeable loss in your video content.
We also get a bonus by using newer codecs, such as H264. They allow for a technique called pixel doubling, so if you compress your video to a size of 320×240, you can stretch or size the video 2x, in this example 640×480. This allows for smaller sizes but offering a larger format for delivery.
If your video is coming from a analog format, don’t forget to deinterlace your content to remove the banding effect.
Compressing Audio
The other important compression ingredient most of us forget, is compressing our audio. For audio you want to make sure you :
- Down sample the audio from stereo to mono
- Switch from 44khz to 22khz
- Use the MP3 codec at 64 kbit/s for the bit rate.
This will give you a much smaller size and still have great quality content.
Hope that helps, I’ll jump into some additional details, tools and post some samples.
